Screw form anchor device

ABSTRACT

A screw form anchor device ( 10 ) intended for screwed penetration into a host material. The anchor device ( 10 ) includes a body ( 11 ) having a manipulating end ( 12 ) and a distal end ( 13 ). A screw thread ( 22 ) is formed by a plurality of tapering angular helix thread forms ( 22   a ) which extend from the distal end. Each angular helix thread form ( 22   a ) has an outward facing surface ( 24 ) and, relative to the distal end, a downward facing surface ( 25 ). In the preferred form an emergent helix thread ( 26 ) commences from a point distant from the distal end ( 13 ). This emergent helix thread ( 26 ) extends toward the manipulating end ( 12 ) of the body ( 11 ).

BACKGROUND TO THE INVENTION

The present invention relates to improvements in anchor devices.

It is known to provide an anchor device based on a self-tapping screwdesign. Such an anchor device being based on a tapered helix ramp beginsto lose its penetrative and anchorage properties as the material (the“host material”) into which it is screwed becomes harder, less elasticand/or fibrous.

A conventional self-tapping screw has a helix coil that protrudes fromthe body of the screw in the form of fin-like profiles. The fins arepredominantly tapered to be substantially sharp at their outer tips. Thetaper angle of the helix profile fin is usually substantially the sameeither side of the central longitudinal axis of the fin. The spacebetween adjacent fins are generally of a V to a U shape or a transformbetween the two. This transformation is likely to be due to the changein the rising angle of a helix profile necessary to gain a given pitchwith the changing circumference brought about by the taper. The V or Ushape naturally creates a greater total surface per screw perimeter areathan would a straight taper measured at the helix outer perimeter.

As suitable as a tapered helix may be for elastic and fibrous hostmaterials, it becomes less suitable as the host material becomes harder,less elastic and/or fibrous.

There are two primary and often interlinked reasons why conventionalself-tapping screw design anchors fail. On the one hand failure canoccur when unsustainable demands are placed on the inward penetrationforces, screw turning forces and screw strength. On the other hand,failure can result when the helix thread path is broken or stripped.

Likely cause and effects involved in failure of a self-tapping screwdesign anchor include:

The top to bottom cavity spaces and surface areas between helixes becomean entrapment for host material. The material must be transformed fromits in situ state into a state of elasticity or fluidity which underpressure begins to adhere to the surface area. The fluidity may be dueto host material elasticity or movement of broken down, granulated hostmaterials or combinations of the two.

Harder host materials create higher volume displacement resistance tothe penetration of the anchor and upward forces act against the helix orthread path. This upward force combines with a twisting and expansiveforce versus directional motion force relative to the axis of the screwwhich deforms the host material into a fluid-like moving state. Thegreater surface area of the entrapping V or U shape causes the hostmaterial to adhere to the surface area. The rotary movement of the screwpenetration thus demands a sheer between the screw and the host materialrelative to directional motion and forces.

Forces occurring internally within the host material, screw and hostmaterial strength and helix design thus determine the limitation of aself-tapping screw for a particular host material.

Host material without fibre, or at a force beyond adequate fibre supportallows the helix encased host material to adhere to the screw and toform a shear line of least resistance that inevitably forms an upwardexpanding conical shape. Should the screw helix design and strength begreater than the host material under the forces applied then the hostmaterial would shear at the upward expanding cone shape defined by theouter perimeter of the helix or helixes. Should the host material be thestronger the forces may be sufficient for the helix to sheer at the bodyof the screw thus resulting in a stripping of the threaded path.Alternatively, random spaces between the screw body and the helixperimeter the shear line will pass through both helix and host materialand strip.

A further cause of screw failure can arise from volume displacementresistance. Harder materials have the strength at volume or distance to“float” up or resist the penetration of the volume of the anchor device.The directional force of volume displacement resistance both influencesthe direction of shear and the effect it has on shearing the helix pathsuch that the screwed rotation breaks away a carrot shaped cone and thehelix path leading to failure. Elastic and fibrous materials createfriction resistance to turning mostly by sideways forces. Experienceshows that volume displacement forces in soils and soft fissil is theprime cause of stripping.

SUMMARY OF THE INVENTION

An object of the present invention is thus to provide a screw formanchor device which provides better control of the forces that governwhat the screw and the host material must endure to function when hostmaterials become stronger, harder, less flexible and less fibrous.

According in one broad aspect of the invention there is provided a screwform anchor device including a body having a manipulating end and adistal end, a screw thread formed by a plurality of tapering angularhelix thread forms extending away from said distal end toward saidmanipulating end, each angular helix thread form having an outwardfacing surface and, relative to the distal end, a downward facingsurface. In one form of the invention an emergent helix thread commencesfrom a point distant from the distal end and extends toward themanipulating end. The emergent helix thread can be continuous ordiscontinuous.

In the preferred form of the invention the outward facing surface isdirected upwardly relative to the distal end. The downward facingsurface is substantially normal to a longitudinal axis of symmetry ofthe body. In the preferred form the distal end of the body is pointed.The emergent helix can be derived from one of said plurality of helixthread forms.

The emergent helix thread preferably has an outward and upward facingperipheral surface for at least part of its length. Preferably theemergent helix thread has an outward and downward facing peripheralsurface as the emergent helix thread approaches a terminal end remotefrom the distal end.

According to one form of the invention one or more of said helix threadsof the helix thread form can merge at a point distant from said distalend. Such merging can occur prior to or after the commencement of theemergent helix thread.

One form of the invention has the helix thread form discontinuing at apoint after commencement of the emergent helix thread.

The emergent helix thread can be of a tapering or substantially constantperipheral diameter or a combination of both.

In one form of the invention the body is joined at the manipulating endby an extension body which includes a helix thread. A multiplicity ofsaid extension bodies may be provided and joined longitudinally end toend relative to the anchor device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective illustration of the anchor device according toone form of the invention when combined with a tool suitable forinserting the anchor device into a host material,

FIG. 2 is an enlarged perspective view of the anchor device as shown inFIG. 1,

FIG. 3 is a side perspective view of a further form of the anchor deviceas shown in FIGS. 1 and 2,

FIG. 4 is a different side perspective of the anchor device of FIG. 3,

FIG. 5 is perspective view of the anchor device but showing only theL-screw as hereinafter described,

FIG. 6 is a perspective view of a fourth embodiment of the anchor deviceaccording to the present invention,

FIG. 7 is an illustration of an anchor device of a type as shown in FIG.6 when inserted into a host material,

FIG. 8 is a modified form of the anchor device as shown in FIGS. 1 and2,

FIG. 9 depicts a framework or structures supported by anchor devicesaccording to the present invention,

FIG. 10 shows superimposed on an illustration of a fence line a postanchorable by an anchor device of the present invention,

FIG. 11 is an illustration of an embodiment of the arrangement shown inFIG. 7,

FIG. 12 depicts an eye screw incorporating the present invention,

FIG. 13 is an illustration of a pole or tower in conjunction with a baseanchored by anchor devices according to the present invention,

FIG. 14 is a further view, perspective in form, of an anchor device ofthe type shown in FIG. 8,

FIG. 15 is a further embodiment of the anchor device showing the use ofa discontinuous emergent helix,

FIG. 16 is a perspective view of a short helix form mountable with thebody to form a discontinuous emergent helix of the type shown in FIG.15, and

FIG. 17 is a further perspective view of the short helix of FIG. 16.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring firstly to FIGS. 1 and 2 there is shown an anchor device 10comprising a body 11 having a manipulating end 12 and a distal orpointed end 13. The manipulating end 12 has a form whereby a force toenable rotation of the device 10 about its central longitudinal axis 15can be applied.

This rotational action can, for example, be applied by a tool 16 of atype illustrated by way of example in FIG. 1. As shown, the tool 16 cancomprise a body 17 with a laterally extending (preferably removable)handle 19 at one end. The other end of the body 17 can have an opening18 into which end 12 of anchor device 10 can engage. In the preferredform, end 12 of the anchor device 10 has an angular cross-sectionalshape which is at least in part replicated by the shape of opening 18.Thus, when end 12 is in opening 18 an angular movement about thelongitudinal axis of body 17 is translated into a rotational movement ofthe anchor 10 about axis 15.

In the preferred form of the invention a flexible member 20 anchoredthrough an opening 14 in end 12 can extend through body 17 (whichpreferably is hollow) to terminate in, say, a tab or plate 21.

If desired, relative longitudinal movement between the anchor device 10and the body 16 can be prevented by a suitable fastener (not shown)inserted through opening 18′ adjacent the end of body 17 into which thepart 12 of the anchor device 10 engages. This fastener can engage with asurface, recess or the like 12′ in part 12 to thereby prevent relativelongitudinal movement between part 12 and body 17 from occurring.

In one form of the invention the anchor device can be inserted into thehost material (ie the ground) by use of tool 16 and become buried withinthe ground up to a depth as may be desired. The depth may be limited bythe available length of tool body 17 if the anchor device is to beburied deep. The tool body 17 (provided that it has not been fixed toanchor 10 by the fastener through opening 18) can then be withdrawnleaving the flexible element 20 in the ground with tab or plate 21 aboveground level for attachment to whatever is required to be anchored. Forexample, a flexible element or the like would be coupled to plate 21such as when the anchor device is to anchor a guy rope, tether or thelike.

However, in the event that tool body 17 is fixed in place to the anchordevice 10 the tool body 17 remains within the ground though handle 19 insuch a situation would be removed thereby permitting the attachment tobody 17 of whatever requires anchorage. Alternatively, body 17 couldform part of the structure to be anchored or supported.

By threading the flexible member 20 through the hollow tool 16 andholding flexible member 20 taut whilst manipulating the tool down themember 20 as a guide it is possible to locate body 17 so that itre-engages with part 12 of the anchor device 10. This enables a turningaction to be applied in reverse manner to the anchor device so that itcan be screwed out of the host material.

Referring now to FIG. 2, the basic construction of the anchor device 10is shown. An L-screw 22 is applied to the body 11 and is formed by aplurality of angular helix threads 22 a extending from the distal end 13for a length along the body 11. The L-screw 22 is tapered with each ofthe plurality of angular threads 22 a each having an upward and outwardfacing (the direction being indicated by arrow 23) helix surface 24 perpitch. L-screw 22 thus has several angular helixes 22 a per pitch whichare arranged to coil up the taper with a step-like appearance whenviewed normal to the longitudinal axis of symmetry 15 of body 10. Thehelixes 22 a therefore take on the appearance of a cut in the surface ofthe body 10 and consequently have a downward surface 25 which is nearright angles to the upward and outward surface 24.

Preferably, and as shown in the detail in FIG. 7, all vertices of thehelix threads are rounded to eliminate subprotrusions and minimisesurface area as much as practical.

As shown, each angular helix thread 22 a begins at the pointed distalend 13 as a shallow cut groove at a fast rising angle to match theconstant pitch of a larger circumference.

According to the present invention, a helix thread 26 can emergeoutwardly from the L-screw 22 to form a conventional spiral helix (the“emergent helix”) with an outward and upward peripheral edge surface 27(the direction being indicated by arrow 28). Alternatively, it maytransform totally into a conventional helix. Surface 29 of helix 26substantially corresponds with the downwardly facing surface 25 of thehelixes of L-screw 22.

The L-screw 22 (other than that shown in FIG. 8) is intended for mediumto hard soils and accordingly as shown can have four to eight helixesper thread pitch. This is by way of example only and more than eight orless than four helix threads 22 a can be used. It maintains all “samepitch” helixes in a “stepped cut” helix arrangement as shown. After aselect amount of revolution and progress up the body a helix begins toemerge into a profile above the others thereby forming the emergenthelix 26. The emergent helix 26 retains a reducing substantially flat“outward and upward” direction of the peripheral surface 27 until itreaches a maximum circumference at which it is transformed into asubstantially pointed or more conventional helix edge 26 a.

As is shown, for example, in FIG. 2 the three non-emerging helixes 22 aof the L-screw 22 ultimately merge inwardly at 24 a into the body 11.

Two helixes 22 a of the L-screw 22 may merge into one helix 22 b (FIG.14) as the taper diameter increases thereby allowing deeper cuts withoutweakening the strength of the anchor device. Merging may be by way ofemerging a helix surface from a cut state to a proud state, eg anemergent helix 26. Alternatively, merging can be by way of emergingouter helix to align a surface 24 with a surface 24 of a higher helixthereby resulting in the two helixes uniting to form a larger helix 32.

In yet a further form a helix surface may be merged inwardly to alignwith that of a lower helix.

The references to upper and lower (or the like) are in reference to thepointed end of the anchor device being “lowermost” and the manipulatingend “uppermost”.

A helix of the L-screw 22 above an emergent helix 26 may merge with thelower helix to form a merge 30 (see FIG. 6) so as to eliminate anentrapment space of large surface area for host material. As also shownin FIG. 6, an emergent helix 26 (whether or not it may be inconventional form) may continue upward along the body 10 for anindefinite length. FIG. 6 furthermore shows a modified form of the endpart 12 to provide a different anchorage and drive fitting.

FIG. 6, therefore, is an illustration of the scope of embodiments whichcan be employed in accordance with the invention as it shows an anchorhaving no set distribution of helixes. As can be seen, an L-screw 22extends from the distal end 13 and incorporates an emerged helix 26 withthe helix 24 continuing above the emerged helix 26 to merge into thebody 11 at 24 a. FIG. 6 also shows how some helixes can be merged outand then started again at an expanding shoulder as cuts 22′ (eg as shownat 31).

FIG. 7 provides an illustration of the anchor device 10 and moreparticularly in profile when cut in section along the longitudinal axis15 to show the applied forces and pressures in the host material. Thedensities of the material show a heart-shaped pressure zone applied tothe material from the turning helix surfaces marked as arrows A andrelief as indicated at B. It also shows the decreased cross-sectionalarea of the body at 11′ and 11″.

FIG. 8 shows yet a further embodiment. This time the anchor device isshown in cross-sectional profile, this particular embodiment may, forexample, be an earth nail for stabilising unstable earth or it may be afixing screw to fix together various laminations of building products.Such products may have one or more layers of hard concrete-like materialor materials that have lesser properties of supportable fibre andelasticity combinations.

The multiple and less deep cut helix (shown in dashed lines) providesfor starting a helix close to point 13 without undue weakening of body10 contribute to helix path and minimise penetration resistance for hostmaterials like concrete, stones, ice or man-made hard materials.

Once again, FIG. 8 shows the cut surface forming helix 22 extending frompoint 13 to merge at 32 into a single helix. The taper of the body 11 isindicated by dotted line T.

Keyed into the body 10 is an extension 33 of generally circularcross-section with a conventional helix 34. As shown, body 33 can havean axially extending projection 35 which is of angular cross-section andengages in a recess in body 10 which is of commensurate shape with theprojection 35. A pin 37 or the like can engage through body 10 and henceprojection 35 to lock the keyed end of body 33 onto the anchor device10.

It will be appreciated by those skilled in the art that a multiple ofbody 33 could be end to end keyed and joined together to provide arequired length.

The total surface area of the tapered “T” conical body portion intowhich the L-screw 22 is formed together with the emergent helix 26 isless than that of conventional helix screw anchor devices. The presentinvention thus has a lesser initial self-tapping screw helix protrusionthan is conventional as it is preferred to secure the helix pitch pathor thread path into the host material. Accordingly, the outward andupward shear surfaces are of maximised area and minimised surroundingentrapments to host material contrary to the situation with aconventional outward biting helix. As with any self-tapping screw theanchor device of the present invention firstly depends on maintainingits threaded path penetration in order to function.

The upper emergent helix 26 adds anchorage from shearing surfacesalready established as helix paths in the soil by the L-screw 22. Thisprovides a greater anchorage/support than is otherwise available withconventional helix screw anchor devices.

Accordingly, the L-screw 22 provides the prime expanding penetration andestablishes a helix path for the emergent helix. Hence the moreconventional helix which follows L-screw 22 engage into the hostmaterial at a greater “depth” thereby enabling the anchorage device ofthe present invention to be used in host materials which previouslycould not conveniently be “self-tapped”.

FIGS. 9 to 13 provide illustrations of different end uses of an anchordevice of any one of the forms described herein. For example, FIG. 9depicts a frame or tower 38 structure having lower or foot portionscoupled to anchor devices 10. This attachment can be provided byextension or mounting pieces 39 coupled in a suitable manner to feet 40.

The extensions 39 can be in the form of a body 17 as shown in FIG. 1 andinstalled with an manipulating arm or crosspiece or similar tool 19′.

The anchor device has particular application for fence posts or poles ofa fence line L. Each post P can be of a suitable form for the requiredend purposes and can, for example, include a multiplicity of openings 41through which wires W can be engaged. The lower end 42 of post P canengage with a base plate 43 which is fixed to the anchor device 10 wheninstalled in the ground.

FIG. 11 depicts an extendable screw shaft suitable for earthstabilisation, underground pipe installations or the like while FIG. 12depicts a typical eye screw which can be used for masonry-likematerials. A bar driver can be placed through the hole 44 in the eyescrew E to apply a rotational movement along the longitudinal axis ofthe anchor device 10 to enable the eye screw to be inserted into allmanner of host materials even up to icebergs to enable a ship's line tobe fastened thereto.

Finally, FIG. 13 depicts a pole or tower base 45 with anchor devicesextending into host material M. The manipulative end parts 12 of theanchor devices 10 can be located in cavities 46 which are then filledwith a suitable filling material 47.

FIG. 14 is a further illustration of the anchor device in the form shownin FIG. 7. This illustrates the pointed distal end of 13 of the body 11has a helix screw 22 formed by a multiplicity of angular screw threadforms 22 a extending away from the pointed end 13. A number of thethreads 22 a merging to form continuing threads 22 b having a wideroutwardly and upwardly facing surface 24. It also illustrates theemergent thread 26 which extends beyond the terminal end of the last ofthe angular threads 22 a. In this form of the invention, however, theperipheral edge of the emergent thread has a surface 27 which isoutwardly and upwardly directed (as previously described) but thistransforms into a peripheral edge surface 27 a toward the upper terminalend of the emergent thread which is outwardly and downwardly projecting.

A further embodiment of the invention is shown with reference to FIGS.15-17 where the emergent thread 26 is formed by short thread sections 50(see FIGS. 16 and 17) which projects outwardly from the surface of thebody 11 toward the manipulating end 12. These short thread sections 50can be so located as to effectively form a helix thread but one which isdiscontinuous as can be seen in FIG. 15.

As with the arrangement shown in FIG. 14 the peripheral edge of theseshort thread sections can be outwardly and upwardly inclined oroutwardly and downwardly inclined though as more preferably shown inFIG. 17 each thread section can have a peripheral edge 51 whichtransforms from an outwardly and upwardly directed surface 52 tooutwardly and downwardly directed surface 53.

By the use of a multiplicity of angular helixes on a constant pitchextending from the pointed tip end of the anchor device the penetratingvolume of the tip is minimised relative to the total volume ofdisplacement of the host material when the anchor device is screwed intothe host material. A lower resistant to initial tip penetration is thusachievable over existing anchor devices of a self tapping type.

The use of the multiplicity of angular helixes leads to a lessening offrictional edges and adhesion of materials which enables the hostmaterial to start sliding on the resultant lead-in surface of the anchordevice. It has been found, for example, that with an anchor deviceformed of plastic with eight angular helixes extending from the tip perpitch there is a considerable increase in overall performance of theanchor device.

The sliding of host material on the angular helix surfaces whileappearing to run more up and down than around like a conventional helix,nevertheless contribute to the controlled directional force undercompression that retains shear strength of the non-fibrous host materialthat it is otherwise diminished with fluid movement of the hostmaterial. The direction of the force begins as downward and is convertedto upward and outward as the taper of the body expands and the pitchforms a conventional helix with the angular helix surface continuing tosmoothly reduce friction and rotational effort of the anchor device.

The merging of the angular helixes conveniently enables deeper cutswhere the strength of the tip is supported by the expanding conediameter somewhat proportionately to strain on the material of theanchor device. This creates an ever widening smooth slipping surface tocontinue the slippage and an increasing, proportionately with body taperdiameter, an area (or bulk block) of this material under pressure thatretains higher than usual shear resistance. The bulk block progresses inan upward and outward direction in the material to combat the downwardresistant of the tip penetration.

This configuration may be continued until a selected size of taperexpansion is considered adequate for the desired end use or hostmaterial type to create a self-supporting thread path. This results inthe lowest possible turning force of the anchor device. The anchorageeffect achieved by use of the anchor device may be increased (whether itbe to resist pulling out of the anchor or pushing the anchor devicefurther into the host material) by an emergent conventional helix orhelixes.

The emergent helix may merge back into the shaft at any interval orspacing. Where the expanded volume of the cut helix taper is consideredinsufficient to relieve the pressure on the straight shafted area of thebody or an entrapment area may form the helix can merge back into thebody before an entrapment is formed. Any adherence of host material tothe helixes may cause breakage of the host material at the outerperimeter of the helix and create a thread stripping.

The helixes may be restarted at the given pitch at later and higherlevels with spacing of both distance and height so as to reduce thetearing out of host material by entrapments and/or surface adhesion. Bythe use of short helix elements spaced radially apart one short helixelement can be located to not be aligned at the same radial directionwith a height spacing between radially aligned entrapments.

The short helix elements may appear similar to a propeller blade and canhave a rising circumference angle out from the body of the anchor deviceto ease turning effort in the host material. The rising angle haspreferably an outer angle flattening surface directing contactingmaterial it may encounter by screwing, upward and downward on thedownward direction side, and a flatter surface angle direction ofdownward and outward on the upper slope of the returning and reducingdiameter side towards the body of the anchor device.

When requiring the anchor device to be reusable and thereby achievefavourable characteristics of screwing out of the host material therising taper volume and any helix should not rise above that of the bodyof the anchor device and helix (if any). The reusable anchor device mayhave a rising volume at the top of the taper greater than the body andhave the cut helixes blend from upward and outward facing to downwardand outward facing such that removal after compaction or consolidationis managed by the same surface forces as used to insert the anchordevice.

What is claimed is:
 1. A screw form anchor device, comprising: a bodyhaving a manipulating end and a distal end; a screw thread formed by aplurality of tapering angular helix thread forms extending away fromsaid distal end toward said manipulating end, each of said helix threadforms having an outward facing surface and, relative to said distal end,a downward facing surface; and an emergent helix thread derived from oneof said plurality of helix thread forms, said emergent helix threadcommencing from a point distant from said distal end and extendingtoward said manipulating end, said emergent helix thread taperingoutwardly to a distal peripheral edge.
 2. The anchor device as claimedin claim 1, wherein the outward facing surface is directed upwardly,relative to said distal end.
 3. The anchor device as claimed in claim 2,wherein the downward facing surface is substantially normal to alongitudinal axis of symmetry of the body.
 4. The anchor device asclaimed in claim 3, wherein the distal end is pointed.
 5. The anchordevice as claimed in claim 3, wherein all vertices associated with eachof the angular helix, thread forms and the emergent helix thread arerounded.
 6. The anchor device as claimed in claim 1, wherein a number ofthe angular helix forms ceases to exist as the cross-sectional diameterof the body increases.
 7. The anchor device as claimed in claim 6,wherein a number of the angular helix thread forms decreases toward themanipulating end by merging of two or more of the angular helix threadforms into a single angular helix thread.
 8. The anchor device asclaimed in claim 7, wherein said merging can occur prior to or after thecommencement of the emergent helix thread.
 9. The anchor device asclaimed in claim 1, wherein the emergent helix thread has an outward andupward facing peripheral edge for at least a part of its length.
 10. Theanchor device as claimed in claim 9, wherein the emergent helix threadhas an outward and downward facing peripheral edge as the emergent helixthread approaches a terminal end remote from said distal end.
 11. Theanchor device as claimed in claim 1, wherein the emergent helix threadis continuous.
 12. The anchor device as claimed in claim 1, where theemergent helix thread is discontinuous.
 13. The anchor device as claimedin claim 1, wherein the emergent helix thread is of tapering orsubstantially constant peripheral diameter or a combination of both. 14.The anchor device as claimed in claim 1, wherein the body is joined atthe manipulating end by an extension body which includes a helix thread.15. The anchor device as claimed in claim 14, wherein a multiplicity ofextension bodies are joined longitudinally end to end relative to theanchor device.
 16. The anchor device as claimed in claim 1, wherein themanipulating end is configured to be engageable by a tool whereby arotational force can be applied to the body.
 17. The anchor device asclaimed in claim 1, therein the emergent helix thread is formed by aplurality of separate thread sections.
 18. The anchor device as claimedin claim 17, wherein each of the thread sections has a peripheral edgewhich transforms over the length thereof from an outwardly and upwardlydirected surface to an outwardly and downwardly directed surface.
 19. Ascrew form anchor device, comprising: a body having a manipulating endand a distal end; a screw thread formed by a plurality of taperingangular helix thread forms extending away from said distal end towardsaid manipulating end, each of said helix thread forms having an outwardfacing surface and, relative to the distal end, a downward facingsurface; and an emergent helix thread derived from one of said pluralityof helix thread forms, said emergent helix thread commencing from apoint distant from said distal end and extending toward saidmanipulating end beyond a terminal end of said angular helix threadforms.
 20. The anchor device as claimed in claim 19, wherein thedownward facing surface is substantially normal to a longitudinal axisof symmetry of the body.
 21. The anchor device as claimed in claim 19,wherein a number of said angular helix thread forms ceases to exist as across-sectional diameter of said body increases.
 22. The anchor deviceas claimed in claim 19, wherein said emergent helix thread has anoutward and upward facing peripheral edge for at least a part of itslength.
 23. The anchor device as claimed in claim 22, wherein saidemergent helix thread has an outward and downward facing peripheral edgeas said emergent helix thread approaches a terminal end remote from saiddistal end.
 24. The anchor device as claimed in claim 19, wherein saidemergent helix thread is continuous.
 25. The anchor device as claimed inclaim 19, wherein said emergent helix thread is discontinuous.
 26. Theanchor device as claimed in claim 19, wherein all vertices associatedwith each of said angular helix thread forms and said emergent threadare rounded.
 27. The anchor device as claimed in claim 19, wherein anumber of said angular helix thread forms decreases toward saidmanipulating end by merging of two or more of said angular helix threadforms into a single angular helix thread.
 28. The anchor device asclaimed in claim 27, wherein said merging occurs prior to or after thecommencement of said emergent helix thread.
 29. The anchor device asclaimed in claim 19, wherein said emergent helix thread is of a taperingor a substantially constant peripheral diameter or a combination ofboth.
 30. The anchor device as claimed in claim 19, wherein said body isjoined at said manipulating end by an extension body which includes ahelix thread.
 31. The anchor device as claimed in claim 19, wherein saidemergent thread is formed by a plurality of separate thread sections.32. The anchor device as claimed in claim 31, wherein each of saidthread sections has a peripheral edge which transforms over a lengththereof from an outwardly and upwardly directed surface to an outwardlyand downwardly directed surface.
 33. A screw form anchor devicecomprising: a body having a manipulating end and a pointed tip end; ascrew thread formed by a plurality of tapering angular helix threadforms extending from said pointed tip end toward said manipulating end,each of said angular helix thread forms having, relative to said pointedtip end, an outward facing surface and a downward facing surface, saidoutward facing surface being tapered upwardly, relative to said pointedtip end; and an emergent helix thread that commences from a pointdistant from said pointed tip end and extends toward said manipulatingend.
 34. The anchor device as claimed in claim 33, wherein said emergenthelix thread is derived from one of said plurality of angular helixthread forms.
 35. The anchor device as claimed in claim 33, wherein saidemergent helix thread tapers outwardly to a distal peripheral edge. 36.The anchor device as claimed in claim 33, wherein said emergent helixthread has an outward and upward facing peripheral edge for at least apart of its length.
 37. The anchor device as claimed in claim 33,wherein said emergent helix thread has an outward and downward facingperipheral edge as said emergent helix thread approaches a terminal endremote from said pointed tip end.
 38. The anchor device as claimed inclaim 33, wherein said emergent helix thread is continuous.
 39. Theanchor device as claimed in claim 33, wherein said emergent helix threadis discontinuous.
 40. The anchor device as claimed in claim 33, whereinall vertices associated with each of said angular helix thread forms andsaid emergent thread are rounded.
 41. The anchor device as claimed inclaim 33, wherein a number of said angular helix thread forms decreasestoward said manipulating end by merging of two or more of said angularhelix thread forms into a single angular helix thread.
 42. The anchordevice as claimed in claim 41, wherein said merging occurs prior to orafter commencement of said emergent helix thread.
 43. The anchor deviceas claimed in claim 33, wherein said emergent helix thread is of atapering or a substantially constant peripheral diameter or acombination of both.
 44. The anchor device as claimed in claim 33,wherein said emergent thread is formed by a plurality of separate threadsections.
 45. The anchor device as claimed in claim 44, wherein each ofsaid thread sections has a peripheral edge which transforms over alength thereof from an outwardly and upwardly directed surface to anoutwardly and downwardly directed surface.